Controlling multiple modems in a wireless terminal using dynamically varying modem transmit power limits

ABSTRACT

A mobile wireless terminal (MWT) includes multiple wireless modems. The multiple modems have their respective transmit outputs combined together to produce an aggregate transmit output. The multiple modems can concurrently transmit data in a reverse link direction and receive data in a forward link direction. The MWT is constrained to operate under an aggregate transmit power limit. Each of the multiple modems has an individual transmit limit related to the aggregate transmit power limit. An MWT controller adjusts the individual transmit power limits in the multiple modems based on an aggregate transmit power limit of the MWT and respective transmit power estimates from the modems, to cause each individual transmit power limit to track a corresponding individual modem transmit power.

CLAIM OF PRIORITY UNDER 35 U.S.C. §120

The present Application for Patent is a Continuation and claims priorityto patent application Ser. No. 10/283,934 entitled “CONTROLLING MULTIPLEMODEMS IN A WIRELESS TERMINAL USING DYNAMICALLY VARYING MODEM TRANSMITPOWER LIMITS” filed Oct. 29, 2002 now U.S. Pat. No. 7,016,697, andassigned to the assignee hereof and hereby expressly incorporated byreference herein.

REFERENCE TO CO-PENDING APPLICATION FOR PATENT

This application is related to commonly-owned applications, both filedon Oct. 29, 2002, entitled “Wireless Terminal Operating Under AnAggregate Transmit Power Limit Using Multiple Modems Having FixedIndividual Transmit Power Limits” having U.S. application Ser. No.10/283,676, and “Controlling Multiple Modems In A Wireless TerminalUsing Energy-Per-Bit Determinations” having U.S. application Ser. No.10/283,935, which are incorporated herein by reference.

BACKGROUND

1. Field

The present invention relates generally to mobile wireless terminals,and particularly, to mobile wireless terminals having multiple modemswhich are constrained to operate under an aggregate transmit power limitfor all of the modems.

2. Background

In a data call established between a mobile wireless terminal (mwt) anda remote station, the mwt can transmit data to the remote station over a“reverse” communication link. Also, the mwt can receive data from theremote station over a “forward” communication link. There is an everpressing need to increase the transmit and receive bandwidth, that is,the data rates, available over both the forward and reverse links.

Typically, the mwt includes a transmit power amplifier to power-amplifya radio frequency (rf) input signal. The power amplifier produces anamplified, rf output signal having an output power responsive to theinput power of the input signal. An inordinately high input power mayover-drive the power amplifier, and thus cause the output power toexceed an acceptable operating transmit power limit of the poweramplifier. In turn, this may cause undesired distortion of the RF outputsignal, including unacceptable out-of-band RF emissions. Therefore,there is a need to carefully control the input and/or output power ofthe transmit power amplifier in an MWT so as to avoid over-driving thepower amplifier. There is a related need to control the output power asjust mentioned, while minimizing to the extent possible, any reductionof the forward and reverse link bandwidth (that is, data rates).

SUMMARY

A feature of the present invention is to provide an MWT that maximizesan overall communication bandwidth in both the reverse and forward linkdirections using a plurality of concurrently operating communicationlinks, each associated with a respective one of a plurality ofmodulator-demodulators (modems) of the MWT.

Another feature of the present invention is to provide an MWT thatcombines multiple modulator-demodulator (modem) transmit signals into anaggregate transmit signal (that is, an aggregate reverse link signal) sothat a single transmit power amplifier can be used. This advantageouslyreduces power consumption, cost, and space requirements compared toknown systems using multiple power amplifiers.

Another feature of the present invention is to carefully control anaggregate input and/or output power of the transmit power amplifier,thereby avoiding signal distortion at the power amplifier output. Arelated feature is to control the aggregate input and/or output power insuch a manner as to maximize bandwidth (that is, data through-put) inboth the reverse and forward link directions.

These features are achieved in several ways. First, individual transmitpower limits are established in each of the plurality of modems of theMWT, to limit the respective, individual modem transmit powers. Eachindividual transmit power limit is derived, in part, from an aggregatetransmit power limit for all of the modems. Together, the individualtransmit power limits collectively limit the aggregate transmit power ofall of the modems.

Second, the present invention adjusts the individual transmit powerlimits in the modems of the MWT based on the aggregate transmit powerlimit and respective transmit power estimates from the modems, to causeeach individual modem transmit power limit to track a correspondingindividual modem transmit power. To do this, the present inventioncollects and/or determines modem transmit statistics corresponding to aprevious transmit period or cycle of the MWT. The modem transmitstatistics can include individual modem transmit data rates, individualmodem transmit powers, the aggregate transmit data rate of all of themodems, and an aggregate transmit power for all of the modems combined.

The invention also detects over-limit ones (that is, over-limitindividual members) of the modems. An over-limit modem has an actualtransmit power, or alternatively, a required transmit power, thatexceeds the individual transmit power limit established in the modem. Inresponse to detecting an over-limit modem, the present inventiondetermines new individual modem transmit power limits across the modemsusing the collected statistics, and updates the modems with the newtransmit power limits. The new transmit power limits are calculated soas to avoid over-limit conditions in the modems. The new modem limitsare used in a next transmit cycle of the MWT. The invention repeats theprocess periodically, to update the individual transmit limits overtime.

In the present invention, only active modems are scheduled to transmitdata in the reverse link direction. “Inactive” modems are modems thatare not scheduled to transmit data. However, in the present invention,inactive modems are able to receive data in the forward link direction,thereby maintaining a high forward link through-put in the MWT, evenwhen modems are inactive in the reverse link direction.

The present invention is directed to a method of controlling transmitpower in a data terminal having N wireless modems with their respectivetransmit outputs combined to produce an aggregate transmit output,comprising establishing an individual transmit power limit in each ofthe N modems, scheduling each of a plurality of the N modems to transmitrespective data, receiving a respective, reported transmit powerestimate from each of the N modems, and adjusting the individualtransmit power limits in at least some of the N modems based on theaggregate transmit power limit and the respective transmit powerestimates from the N modems. This causes each individual transmit powerlimit to track a corresponding individual modem transmit power.

The present invention is also directed to an MWT, constrained to operatewithin an aggregate transmit power limit, including a plurality (N) ofwireless modems with their respective transmit outputs combined toproduce an aggregate transmit output. The N modems can concurrentlytransmit data in the reverse link direction and receive data in theforward link direction. One aspect of the present invention is apparatuscomprising means for establishing an individual transmit power limit ineach of the N modems, means for scheduling each of a plurality of the Nmodems to transmit respective data, means for receiving a respective,reported transmit power estimate from each of the N modems, and meansfor adjusting the individual transmit power limits in at least some ofthe N modems based on the aggregate transmit power limit and therespective transmit power estimates from the N modems.

In further aspects, a method and apparatus is provided for derivingmodem transmit limits in a wireless terminal constrained to operatewithin an aggregate transmit power limit, the wireless terminalincluding N wireless modems with their respective transmit outputscombined to produce an aggregate transmit output, the modems havingindividual transmit power limits to limit their respective transmitpowers, the modems reporting respective transmit power estimates. Theapparatus comprises means for determining an aggregate transmit powerencompassing all of the N modems, means for deriving an aggregatetransmit power margin based on a difference between the aggregatetransmit power and the aggregate transmit power limit, and means fordividing the aggregate transmit power margin among the N modems toproduce, for each of the N modems, an individual transmit power limitthat is greater than the corresponding transmit power estimate for eachmodem. This and further aspects of the present invention are describedbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, objects, and advantages of the present invention willbecome more apparent from the detailed description set forth below whentaken in conjunction with the drawings in which like referencecharacters identify the same or similar elements throughout and wherein:

FIG. 1 is an illustration of an example wireless communication system.

FIG. 2 is a block diagram of an example mobile wireless terminal.

FIG. 3 is a block diagram of an example modem representative ofindividual modems of the mobile wireless terminal of FIG. 2.

FIG. 4 is an illustration of an example data frame that may betransmitted or received by any one of the modems of FIGS. 2 and 3.

FIG. 5 is an illustration of an example status report from the modems ofFIGS. 2 and 3.

FIG. 6 is a flowchart of an example method performed by each of themodems of FIGS. 2 and 3.

FIG. 7 is a flowchart of an example method performed by the mobilewireless terminal.

FIG. 8 is a flowchart expanding on the method of FIG. 7.

FIG. 9 is a flowchart expanding on the method of FIG. 7.

FIG. 10 is a flowchart of another example method performed by the mobilewireless terminal.

FIG. 11 is an example plot of Power versus Modem index(i) identifyingrespective ones of the modems of FIG. 2, wherein uniform modem transmitpower limits are depicted. FIG. 11 also represents an example transmitscenario of the mobile wireless terminal of FIG. 2.

FIG. 12 is another example transmit scenario similar to FIG. 11.

FIG. 13 is an illustration of an alternative, tapered arrangement forthe modem transmit power limits.

FIG. 14 is a flowchart of an example method of calibrating modems in themobile wireless terminal of FIG. 2.

FIG. 15 is a flowchart of an example method of operating the mobilewireless terminal, using dynamically updated individual modem transmitpower limits.

FIG. 16 is a flowchart of an example method expanding on the method ofFIG. 15.

FIG. 17 is a flowchart of an example method of determining a maximumnumber of active modems using an average energy-per-transmitted-bit ofthe modems.

FIG. 18 is a flowchart of an example method of determining a maximumnumber of active modems, using an individual energy-per-transmitted-bitfor each of the modems.

FIG. 19 is a graphical representation of different modem transmit limitarrangements.

FIG. 20 is a flowchart of an example method of operating the mobilewireless terminal using dynamically varying individual modem transmitpower limits, so the modem transmit limits track the modem transmitpowers.

FIG. 21 is a flow chart of an example method expanding on the method ofFIG. 20.

FIG. 22 is a flow chart of an example method expanding on the method ofFIG. 21.

FIGS. 23A-23D are example plots of power versus modem index identifyingmodems being controlled in accordance with the method of FIG. 20, fordifferent example transmit scenarios of the mobile wireless terminal ofFIG. 2.

FIG. 24 is a functional block diagram of an example controller of themobile wireless terminal of FIG. 2, for performing the methods of thepresent invention.

DETAILED DESCRIPTION

A variety of multiple access communication systems and techniques havebeen developed for transferring information among a large number ofsystem users. However, spread spectrum modulation techniques, such asthose used in code division multiple access (CDMA) communication systemsprovide significant advantages over other modulation schemes, especiallywhen providing service for a large number of communication system users.Such techniques are disclosed in the teachings of U.S. Pat. No.4,901,307, which issued Feb. 13, 1990 under the title “Spread SpectrumMultiple Access Communication System Using Satellite or TerrestrialRepeaters,” and U.S. Pat. No. 5,691,194, which issued Nov. 25, 1997,entitled “Method and Apparatus for Using Full Spectrum Transmitted Powerin a Spread Spectrum Communication System for Tracking IndividualRecipient Phase Time and Energy,” both of which are assigned to theassignee of the present invention, and are incorporated herein byreference in their entirety.

The method for providing CDMA mobile communications was standardized inthe United States by the Telecommunications Industry Association inTIA/EIA/IS-95-A entitled “Mobile Station-Base Station CompatibilityStandard for Dual-Mode Wideband Spread Spectrum Cellular System,”referred to herein as IS-95. Other communications systems are describedin other standards such as the IMT-2000/UM, or International MobileTelecommunications System 2000/Universal Mobile TelecommunicationsSystem, standards covering what are referred to as wideband CDMA(WCDMA), cdma2000(such as cdma2000 1× or 3× standards, for example) orTD-SCDMA.

I. Example Communication Environment

FIG. 1 is an illustration of an exemplary wireless communication system(WCS) 100 that includes a base station 112, two satellites 116 a and 116b, and two associated gateways (also referred to herein as hubs) 120 aand 120 b. These elements engage in wireless communications with userterminals 124 a, 124 b, and 124 c. Typically, base stations andsatellites/gateways are components of distinct terrestrial and satellitebased communication systems. However, these distinct systems mayinter-operate as an overall communications infrastructure.

Although FIG. 1 illustrates a single base station 112, two satellites116, and two gateways 120, any number of these elements may be employedto achieve a desired communications capacity and geographic scope. Forexample, an exemplary implementation of WCS 100 includes 48 or moresatellites, traveling in eight different orbital planes in Low EarthOrbit (LEO) to service a large number of user terminals 124.

The terms base station and gateway are also sometimes usedinterchangeably, each being a fixed central communication station, withgateways, such as gateways 120, being perceived in the art as highlyspecialized base stations that direct communications through satelliterepeaters while base stations (also sometimes referred to ascell-sites), such as base station 112, use terrestrial antennas todirect communications within surrounding geographical regions.

User terminals 124 each have or include apparatus or a wirelesscommunication device such as, but not limited to, a cellular telephone,wireless handset, a data transceiver, or a paging or positiondetermination receiver. Furthermore each of user terminals 124 can behand-held, portable as in vehicle-mounted (including for example cars,trucks, boats, trains, and planes), or fixed, as desired. For example,FIG. 1 illustrates user terminal 124 a as a fixed telephone or datatransceiver, user terminal 124 b as a hand-held device, and userterminal 124 c as a portable vehicle-mounted device. Wirelesscommunication devices or terminals 124 are also sometimes referred to asmobile wireless terminals, user terminals, mobile wireless communicationdevices, subscriber units, mobile units, mobile stations, mobile radios,or simply “users,” “mobiles,” “terminals,” or “subscribers” in somecommunication systems, depending on preference.

User terminals 124 engage in wireless communications with other elementsin WCS 100 through CDMA communications systems. However, the presentinvention may be employed in systems that employ other communicationstechniques, such as time division multiple access (TDMA), and frequencydivision multiple access (FDMA), or other waveforms or techniques listedabove (WCDMA, CDMA2000 . . . ).

Generally, beams from a beam source, such as base station 112 orsatellites 116, cover different geographical areas in predefinedpatterns. Beams at different frequencies, also referred to as CDMAchannels, frequency division multiplexed (FDM) channels, or “sub-beams,”can be directed to overlap the same region. It is also readilyunderstood by those skilled in the art that beam coverage or serviceareas for multiple satellites, or antenna patterns for multiple basestations, might be designed to overlap completely or partially in agiven region depending on the communication system design and the typeof service being offered, and whether space diversity is being achieved.

FIG. 1 illustrates several exemplary signal paths. For example,communication links 130 a-c provide for the exchange of signals betweenbase station 112 and user terminals 124. Similarly, communications links138 a-d provide for the exchange of signals between satellites 116 anduser terminals 124. Communications between satellites 116 and gateways120 are facilitated by communications links 146 a-d.

User terminals 124 are capable of engaging in bi-directionalcommunications with base station 112 and/or satellites 116. As such,communications links 130 and 138 each include a forward link and areverse link. A forward link conveys information signals to userterminals 124. For terrestrial-based communications in WCS 100, aforward link conveys information signals from base station 112 to a userterminal 124 over a link 130. A satellite-based forward link in thecontext of WCS 100 conveys information from a gateway 120 to a satellite116 over a link 146 and from the satellite 116 to a user terminal 124over a link 138. Thus, terrestrial-based forward links typically involvea single wireless signal path between the user terminal and basestation, while satellite-based forward links typically involve two ormore wireless signal paths between the user terminal and a gatewaythrough at least one satellite (ignoring multipath).

In the context of WCS 100, a reverse link conveys information signalsfrom a user terminal 124 to either a base station 112 or a gateway 120.Similar to forward links in WCS 100, reverse links typically require asingle wireless signal path for terrestrial-based communications and twowireless signal paths for satellite-based communications. WCS 100 mayfeature different communications offerings across these forward links,such as low data rate (LDR) and high data rate (HDR) services. Anexemplary LDR service provides forward links having data rates from 3kilobits per second (kbps) to 9.6 kbps, while an exemplary HDR servicesupports typical data rates as high as 604 kbps and higher.

As described above, WCS 100 performs wireless communications accordingto CDMA techniques. Thus, signals transmitted across the forward andreverse links of links 130, 138, and 146 convey signals that areencoded, spread, and channelized according to CDMA transmissionstandards. In addition, block interleaving can be employed for theseforward and reverse links. These blocks are transmitted in frames havinga predetermined duration, such as 20 milliseconds.

Base station 112, satellites 116, and gateways 120 may adjust the powerof the signals that they transmit over the forward links of WCS 100.This power (referred to herein as forward link transmit power) may bevaried according to user terminal 124 and according to time. This timevarying feature may be employed on a frame-by-frame basis. Such poweradjustments are performed to maintain forward link bit error rates (BER)within specific requirements, reduce interference, and conservetransmission power.

User terminals 124 may adjust the power of the signals that theytransmit over the reverse links of WCS 100, under the control ofgateways 120 or base stations 112. This power (referred to herein asreverse link transmit power) may be varied according to user terminal124 and according to time. This time varying feature may be employed ona frame-by-frame basis. Such power adjustments are performed to maintainreverse link bit error rates (BER) within specific requirements, reduceinterference, and conserve transmission power.

Examples of techniques for exercising power control in suchcommunication systems are found in U.S. Pat. Nos. 5,383,219, entitled“Fast Forward Link Power Control In A Code Division Multiple AccessSystem,” U.S. Pat. No. 5,396,516, entitled “Method And System For TheDynamic Modification Of Control Parameters In A Transmitter PowerControl System,” and U.S. Pat. No. 5,056,109, entitled “Method andApparatus For Controlling Transmission Power In A CDMA Cellular MobileTelephone System,” which are incorporated herein by reference.

II. Mobile Wireless Terminal

FIG. 2 is a block diagram of an example MWT 206 constructed and operatedin accordance with the principles of the present invention. MWT 206communicates wirelessly with a base station or gateway (referred to as aremote station), not shown in FIG. 2. Also, MWT 206 may communicate witha user terminal. MWT 206 receives data from external data sources/sinks,such as a data network, data terminals, and the like, over acommunication link 210, such as an ethernet link, for example. Also, MWT206 sends data to the external data sources/sinks over communicationlink 210.

MWT 206 includes an antenna 208 for transmitting signals to andreceiving signals from the remote station. MWT 206 includes a controller(that is, one or more controllers) 214 coupled to communication link210. Controller 214 exchanges data with a memory/storage unit 215, andinterfaces with a timer 217. Controller 214 providesdata-to-be-transmitted to, and receives data from, a plurality ofwireless modems 216 a-216 n over a plurality of correspondingbi-directional data links 218 a-218 n between controller 214 and modems216. Data connections 218 may be serial data connections. The number Nof modems that may be used can be one of several values, as desired,depending on known design issues such as complexity, cost, and so forth.In an example implementation, N=16.

Wireless modems 216 a-216 n provide RF signals 222 a _(T)-222 n _(T) toand receive RF signals 222 a _(R)-222 n _(R) from a powercombiner/splitter assembly 220, over a plurality of bi-directional RFconnections/cables between the modems and the power combiner/splitterassembly. In a transmit (that is, reverse link) direction, a powercombiner included in assembly 220 combines together the RF signalsreceived from all of modems 216, and provides a combined (that is,aggregate) RF transmit signal 226 to a transmit power amplifier 228.Transmit power amplifier 228 provides an amplified, aggregate RFtransmit signal 230 to a duplexer 232. Duplexer 232 provides theamplified, aggregate RF transmit signal to antenna 208. In MWT 206,duplexing may be achieved by means other than duplexer 232, such asusing separate transmit and receive antennas. Also, a power monitor 234,coupled to an output of power amplifier 228, monitors a power level ofamplified, aggregate transmit signal 230. Power monitor 234 provides asignal 236 indicating the power level of amplified, aggregate transmitsignal 230 to controller 214. In an alternative arrangement of MWT 206,power monitor 234 measures the power level of aggregate signal 226 atthe input to transmit amplifier 228. In this alternative arrangement,the aggregate transmit power limit of MWT 206 is specified at the inputto transmit amplifier 228 instead of at its output, and the methods ofthe present invention, described below, take this into account.

In a receive (that is, forward link) direction, antenna 208 provides areceived signal to duplexer 232. Duplexer 232 routes the received signalto a receive amplifier 240. Receive amplifier 240 provides an amplifiedreceived signal to assembly 220. A power splitter included in assembly220 divides the amplified received signal into a plurality of separatereceived signals and provides each separate signal to a respective oneof the modems 216.

MWT 206 communicates with the remote station over a plurality ofwireless CDMA communication links 250 a-250 n established between MWT206 and the remote station. Each of the communication links 250 isassociated with a respective one of modems 216. Wireless communicationlinks 250 a-250 n can operate concurrently with one another. Each ofwireless communication links 250 supports wireless traffic channels forcarrying data between MWT 206 and the remote station in both forward andreverse link directions. The plurality of wireless communicationchannels 250 form part of an air interface 252 between MWT 206 and theremote station.

In the present embodiment, MWT 206 is constrained to operate under anaggregate transmit power limit (APL) at the output of transmit amplifier228. In other words, MWT 206 is required to limit the transmit power ofsignal 230 to a level that is preferably below the aggregate transmitpower limit. All of modems 216, when transmitting, contribute to theaggregate transmit power of signal 230. Accordingly, the presentinvention includes techniques to control the transmit powers of modems216, and thereby cause the aggregate transmit power of modems 216, asmanifested in transmit signal 230, to be under the aggregate transmitpower limit.

Over-driving transmit amplifier 228 causes the power level of signal 230to exceed the aggregate transmit power limit. Therefore, the presentinvention establishes individual transmit power limits (also referred toas transmit limits) for each of modems 216. The individual transmitpower limits are related to the aggregate transmit power limit in such away as to prevent modems 216 from collectively over-driving transmitamplifier 228. During operation of MWT 206, the present inventiondetects over-limit ones of modems 216. In response to detecting theover-limit modem(s), controller 214 adjusts the individual transmitpower limits in at least some of modems 216 based on the aggregatetransmit power limit and respective transmit power estimates from modems216, to cause each individual modem transmit power limit to track acorresponding individual modem transmit power. An objective is tomaximize bandwidth (that is, transmit data rate) for a given aggregatetransmit power limit by adjusting the individual modem transmit powerlimits. Further aspects of the present invention are described below.

Although MWT 206 is referred to as being mobile, it is to be understoodthat the MWT is not limited to a mobile platform or portable platforms.For example, MWT 206 may reside in a fixed base station or gateway. MWT206 may also reside in a fixed user terminal 124 a.

III. Modem

FIG. 3 is a block diagram of an example modem 300 representative of eachof modems 216. Modem 300 operates in accordance with CDMA principles.Modem 300 includes a data interface 302, a controller 304, a memory 306,a modem signal processor or module 308, such as one or more digitalsignal processors (DSP) or ASICs, an intermediate frequency IF/RFsubsystem 310, and an optional power monitor 312, all coupled to oneanother over a data bus 314. In some systems, the modems do not comprisetransmit and receive processor coupled in pairs as in a more traditionalmodem structure, but may use an array of transmitters and receivers ormodulators and demodulates which are interconnected as desired to handleuser communications, and one or more signals, or otherwise time sharedamong users.

In the transmit direction, controller 304 receivesdata-to-be-transmitted from controller 214 over data connection 218 i(where i indicates any one of the modems 216 a-216 n), and throughinterface 302. Controller 304 provides the data-to-be-transmitted tomodem processor 308. A transmit (Tx) processor 312 of modem processor308 encodes and modulates the data-to-be-transmitted, and packages thedata into data frames that are to be transmitted. Transmit processor 312provides a signal 314 including the data frames to IF/RF subsystem 310.Subsystem 310 frequency up-converts and amplifies signal 314, andprovides a resulting frequency up-converted, amplified signal 222 i _(T)to power combiner/splitter assembly 220. Optional power meter 312monitors a power level of signal 222 i _(T) (that is, the actualtransmit power at which modem 300 transmits the above-mentioned dataframes). Alternatively, modem 300 can determine the modem transmit powerbased on gain/attenuator settings of IF/RF subsystem 310 and the datarate at which modem 300 transmits the data frames.

In the receive direction, IF/RF subsystem 310 receives a received signal222 i _(R) from power combiner/splitter assembly 220, frequencydown-converts signal 222 i _(R) and provides the resulting frequencydown-converted signal 316, including received data frames, to a receive(Rx) processor 318 of modem processor 308. Receive processor 318extracts data from the data frames, and then controller 304 provides theextracted data to controller 214, using interface 302 and dataconnection 218 i.

Modems 216 each transmit and receive data frames in the manner describedabove and further below. FIG. 4 is an illustration of an example dataframe 400 that may be transmitted or received by any one of modems 216.Data frame 400 includes a control or overhead field 402 and a payloadfield 404. Fields 402 and 404 include data bits used to transfer eithercontrol information (402) or payload data (404). Control field 402includes control and header information used in managing a communicationlink established between a respective one of modems 216 and the remotestation. Payload field 404 includes payload data (bits 406), forexample, data-to-be-transmitted between controller 214 and the remotestation during a data call (that is, over the communication linkestablished between the modem and the remote station). For example, datareceived from controller 214, over data link 218 i, is packaged intopayload field 404.

Data frame 400 has a duration T, such as 20 milliseconds, for example.The payload data in payload field 404 is conveyed at one of a pluralityof data rates, including a maximum or full-rate (for example, 9600bits-per-second (bps)), a half-rate (for example, 4800 bps), aquarter-rate (for example, 2400 bps), or an eighth-rate (for example,1200 bps). Each of the modems 216 attempts to transmit data at thefull-rate (that is, at a maximum data rate). However, an over-limitmodem rate-limits, whereby the modem reduces its transmit data rate fromthe maximum rate to a lower rate, as will be discussed below. Also, eachof the modems 216 may transmit a data frame (for example, data frame400) without payload data. This is referred to as a zero-rate dataframe.

In one modem arrangement, each of the data bits 406 within a framecarries a constant amount of energy, regardless of the transmit datarate. That is, within a frame, the energy-per-bit, E_(b), is constantfor all of the different data rates. In this modem arrangement, eachdata frame corresponds to an instantaneous modem transmit power that isproportional to the data rate at which the data frame is transmitted.Therefore, the lower the data rate, the lower the modem transmit power.When transferring data at lower rates the energy of each bit isgenerally spread out over time. That is, for half-rate the bit energy isspread out over twice the length of time, quarter-rate, four times thelength of time, and so forth, By spreading the transmit energy across adata frame in this manner, no energy spikes are caused during portionsof the frame which would exceed the allowed limit.

In addition, when transferring data at lower rates the energy of eachbit is generally spread out over time. That is, for half-rate the bitenergy is spread out over twice the length of time, quarter-rate, fourtimes the length of time, and so forth, By spreading the transmit energyacross a data frame in this manner, no energy spikes are caused duringportions of the frame which would exceed the allowed limit.

Each of the modems 216 provides status reports to controller 214 overrespective data connections 218. FIG. 5 is an illustration of an examplestatus report 500. Status report 500 includes a modem data rate field502, a modem transmit power field 504, and an optional over-limit (alsoreferred to as a rate-limiting) indicator field 506. Each modem reportsthe data rate of the last transmitted data frame in field 502, and thetransmit power of the last transmitted data frame in field 504. Inaddition, each modem can optionally report whether it is in arate-limiting condition in field 506.

In another alternative modem arrangement, the modem can provide statussignals indicating the over-limit/rate-limiting condition, the transmitpower, and transmit data rate of the modem.

IV. Example Method

FIG. 6 is a flowchart of an example method or process 600 representativeof an operation of modem 300, and thus, of each of modems 216. Method600 assumes a data call has been established between a modem (forexample, modem 216 a) and the remote station. That is, a communicationlink including a forward link and a reverse link has been establishedbetween the modem and the remote station.

At a first step 602, a transmit power limit P_(L) is established in themodem (for example, in modem 216 a).

At a next step 604, the modem receives a power control command from theremote station over the forward link indicating a requested transmitpower PR at which the modem is to transmit data frames in the reverselink direction. This command may be in the form of an incremental powerincrease or decrease command.

At a decision step 606, the modem determines whether any payload datahas been received from controller 214, that is, whether or not there isany payload data to transmit to the remote station. If not, processingproceeds to a next step 608. At step 608, the modem transmits a dataframe at the zero-rate, that is, without payload data. The zero-ratedata frame may include control/overhead information used to maintain thecommunication link/data call, for example. The zero-rate data framecorresponds to a minimum transmit power of the modem.

On the other hand, if there is payload data to transmit, then methodprocessing (control) proceeds from step 606 to a next step 610. At step610, the modem determines whether or not it is not over-limit, that is,whether the modem is under-limit. In one arrangement, determiningwhether or not the modem is under-limit includes determining whether therequested transmit power P_(R) is less than the transmit power limitP_(L). In this arrangement, the modem is considered over-limit when therequested transmit power P_(R) is greater than or equal to P_(L). In analternative arrangement, determining whether or not the modem isunder-limit includes determining whether an actual transmit power P_(T)of the modem is less than the transmit power limit P_(L). In thisarrangement, the modem is considered over-limit when P_(T) is greaterthan or equal P_(L). The modem may use power monitor 312 in determiningwhether its transmit power P_(T), for example, the transmit power ofsignal 222 i _(T), is less than the transmit power limit P_(L).

While the modem is not-over limit, the modem transmits a data frame,including payload data and control information, at a maximum data rate(for example, the full-rate) and at a transmit power level P_(T) that isin accordance with the requested transmit power P_(R). In other words,the modem transmit power P_(T) tracks the requested transmit powerP_(R).

When P_(T) or P_(R) is equal to or greater than P_(L), the modem isover-limit, and thus rate-limits from a current rate (for example, thefull-rate) to a lower transmit data rate (for example, to the half-rate,quarter-rate, eighth-rate or even the zero-rate), thereby reducing thetransmit power P_(T) of the modem relative to when the modem wastransmitting at the full-rate. Therefore, rate-limiting in response toeither of the over-limit conditions described above is a form of modemself power-limiting, whereby the modem maintains its transmit powerP_(T) below the transmit power limit P_(L). Also, theover-limit/rate-limiting condition, as reported in status report 500,indicates to controller 214 that the requested power P_(R), or theactual transmit power P_(T) in the alternative arrangement, is greaterthan or equal to the transmit power limit P_(L). It should beappreciated that while the modem may be operating at the zero-rate inthe transmit (that is, reverse link) direction, because it either israte-limiting (for example, in step 610) or has no payload data totransmit (step 608), it may still receive full-rate data frames in thereceive (that is, forward link) direction.

Although it can be advantageous for the modem to self rate-limit inresponse to the over-limit condition, an alternative arrangement of themodem does not rate-limit in this manner. Instead, the modem reports theover-limit condition to controller 214, and then waits for thecontroller to impose rate-limiting adjustments. A preferred arrangementuses both approaches. That is, the modem self rate-limits in response tothe over-limit condition, and the modem reports the over-limit conditionto controller 214, and in response, the controller imposes rate-limitingadjustments on the modem.

After both step 608 and step 610, the modem generates a status report(for example, status report 500) at a step 612, and provides the reportto controller 214 over a respective one of data links 218.

V. Fixed Transmit Power Limit Embodiments

FIG. 7 is a flowchart of an example method performed by MWT 206,accordance with the present embodiments. Method 700 includes aninitializing step 702. Step 702 includes further steps 704, 706, and708. At step 704, controller 214 establishes an individual transmitpower limit P_(L) in each of modems 216. The transmit power limits arefixed over time in method 700.

At step 706, controller 214 establishes a data call over each of modems216. In other words, a communication link, including both forward andreverse links, is established between each of the modems 216 and theremote station. The communication links operate concurrently with oneanother. In an exemplary arrangement of the present invention, thecommunication links are CDMA based communication links.

In the embodiments, a modem may be designated as an active modem or asan inactive modem. Controller 214 can schedule active modems, but notinactive modems, to transmit payload data. Controller 214 maintains alist identifying currently active modems. At a step 708, controller 214initially designates all of the modems as being active, by adding eachof the modems to the active list, for example.

At a next step 710, assuming controller 214 has received data that needsto be transmitted to the remote station, controller 214 schedules eachof the active modems to transmit payload data. In a first past throughstep 710, all of modems 216 are active (from step 708). However, insubsequent passes through step 710, some of modems 216 may be inactive,as will be described below.

Controller 214 maintains a queue of data-to-be-transmitted for each ofthe active modems, and supplies each data queue with data received fromthe external data sources over link 210. Controller 214 provides datafrom each data queue to the respective active modem. Controller 214executes data-loading algorithms to ensure the respective data queuesare generally, relatively evenly loaded, so that each active modem isconcurrently provided with data-to-be-transmitted. After controller 214provides data to each modem, each modem in turn attempts to transmit thedata in data frames at the full-rate and in accordance with therespective requested transmit power P_(R), as described above inconnection with FIG. 6.

At step 710, controller 214 also de-schedules inactive modems bydiverting data-to-be-transmitted away from the inactive modems andtoward the active modems. However, there are no inactive modems in thefirst pass through step 710, since all of the modems are initiallyactive after step 708, as mentioned above.

At a next step 712, controller 214 monitors the modem status reportsfrom all of the inactive and active modems.

At a next step 714, controller 214 determines whether any of the modems216 are over-limit, and thus rate-limiting, based on the modem statusreports. If controller 214 determines that one or more (that is, atleast one) of the modems are over-limit, then controller 214 deactivatesonly these over-limit modems, at a step 716. For example, controller 214can deactivate an over-limit modem by removing it from the active list.

If none of the modems are determined to be over-limit at step 714, themethod or processing proceeds to a step 718. Processing also proceeds tostep 718 after any over-limit modems are deactivated in step 716. Atstep 718, controller 214 determines whether or not any of the modemspreviously deactivated at step 716 need to be activated (that is,reactivated). Several techniques for determining whether modems shouldbe activated are discussed below. If the answer at step 718 is yes(modems need to be reactivated), then processing proceeds to a step 720,and controller 214 activates the previously deactivated modems that needto be activated, for example, by reinstating the modems on the activelist.

If none of the previously deactivated modems need to be activated, thenprocessing proceeds from step 718 back to step 710. Also, processingproceeds from step 720 to step 710. Steps 710 through 720 are repeatedover time, whereby over-limit ones of modems 216 are deactivated at step716 and then reactivated at step 718 as appropriate, and correspondinglyde-scheduled and re-scheduled at step 710.

When an over-limit modem is deactivated at step 716 (that is, becomesinactive), and remains deactivated through step 718, the modem will bedescheduled in the next pass through step 710. In other words,controller 214 will no longer provide data to the deactivated modem.Instead, controller 214 will divert data to active modems. If it isassumed that the data call associated with the deactivated modem has notbeen torn-down (that is, terminated), then de-scheduling the modem atstep 710 will cause the deactivated modem to have no payload data totransmit, and will thus cause the modem to operate at the zero-rate andat a corresponding minimum transmit power level on the reverse link (seesteps 606 and 608, described above in connection with FIG. 6). Thiskeeps the data call alive or active on the deactivated/descheduledmodem, so the modem can still receive full-rate data frames on theforward link. When a data call associated with a modem is torn-down,that is, terminated or ended, the modem stops transmitting and receivingdata altogether.

Deactivating the over-limit modem at step 716 ultimately causes themodem to reduce its transmit data rate and corresponding transmit powerin the reverse link direction. In this manner, controller 214individually controls the modem transmit power limits (and thus modemtransmit powers), and as a result, can maintain the aggregate transmitpower of signal 230 at a level below the aggregate transmit power limitof MWT 206.

Alternative arrangements of method 700 are possible. As described above,deactivating step 716 includes deactivating an over-limit modem bydesignating the modem as inactive, for example, by removing the modemfrom the active list.

Conversely, activating step 720 includes reinstating the deactivatedmodem to the active list. In an alternative arrangement of method 700,deactivating step 716 further includes tearing-down (that is,terminating) the data call (that is, the communication link) associatedwith the over-limit modem. Also in this alternative arrangement,activating step 720 further includes establishing another data call overthe previously deactivated modem, so that the modem can begin totransmit data to and receive data from the remote station.

In another alternative arrangement of method 700, deactivating step 716further includes deactivating all of the modems, whether over-limit ornot over-limit, when any one of the over-limit modems is detected atstep 714. In this arrangement, deactivating the modems may includedesignating all of the modems as inactive, and may further includetearing-down all of the data calls associated with the modems.

FIG. 8 is a flowchart expanding on transmit limit establishing step 704of method 700. At a first step 802, controller 214 derives the transmitpower limit for each of modems 216. For example, controller 214 maycalculate the transmit power limits, or simply access predeterminedlimits stored in a memory look-up table. At a next step 804, controller214 provides each of the modems 216 with a respective one of thetransmit power limits, and in response, the modems store theirrespective transmit power limits in their respective memories.

FIG. 9 is a flowchart expanding on determining step 718 of method 700.Controller 214 monitors (at step 712, for example) the respectivereported transmit powers of the deactivated/inactive modems that aretransmitting at the zero-rate. At a step 902, controller 214 derives,from the reported modem transmit powers, respective extrapolated modemtransmit powers representative of when the modems transmit at themaximum transmit data rate.

At a next step 904, controller 214 determines whether each extrapolatedtransmit power is less than the respective modem transmit power limitP_(L). If yes, then processing proceeds to step 720 where the respectivemodem is activated, because it is likely the modem will not exceed thepower limit. If not, the modem remains deactivated, and flow of themethod proceeds back to step 710.

FIG. 10 is a flowchart of another example method 1000 performed by MWT206. Method 1000 includes many of the method steps described previouslyin connection with FIG. 7, and such method steps will not be describedagain. However, method 1000 includes a new step 1004 following step 716,and a corresponding determining step 1006. At step 1004, controller 214initiates an activation timeout period (for example, using timer 217)corresponding to each modem deactivated at step 716. Alternatively,controller 214 can schedule a future activation time/event correspondingto each modem deactivated in step 716.

At determining step 1006, controller 214 determines whether it is timeto activate any of the previously deactivated modems. For example,controller 214 determines whether any of the activation timeout periodshave expired, thereby indicating it is time to activate thecorresponding deactivated modem. Alternatively, controller 214determines whether the activation time/event scheduled at step 1004 hasarrived.

Alternative arrangements of method 1000, similar to the alternativearrangements discussed above in connection with method 700, are alsoenvisioned.

VI. Fixed Transmit Power Limit Arrangements

1. Uniform Limits

In one fixed limit arrangement, a uniform set of fixed transmit powerlimits is established across all of modems 216. That is, each modem hasthe same transmit power limit as each of the other modems. FIG. 11 is anexample plot of Power versus Modem index(i) identifying respective onesof the modems 216, wherein uniform, modem transmit power limits P_(Li)are depicted. As depicted in FIG. 11, modem(1) corresponds to powerlimit P_(L1), modem(2) corresponds to power limit P_(L2), and so on.

In one arrangement of uniform limits, each transmit power limit P_(L) isequal to the aggregate transmit power limit APL divided by the totalnumber N of modems 216. Under this arrangement of uniform limits, whenall of the modems have respective transmit powers equal to theirrespective transmit power limits, the aggregate transmit power for allof the modems will just meet, and not exceed, the APL. An example APL inthe present invention is approximately 10 or 11 decibel-Watts (dBW).

FIG. 11 also represents an example transmit scenario for MWT 206.Depicted in FIG. 11 are representative, requested modem transmit powersP_(R1) and P_(R2) corresponding to modem(1) and modem(2). The exampletransmit scenario depicted in FIG. 11 corresponds to the scenario inwhich all of the requested modem transmit powers are below therespective, uniform transmit power limits. In this situation, none ofthe modems are over-limit, and thus rate-limiting.

FIG. 12 is another example transmit scenario similar to FIG. 11, exceptthat modem(2) has a requested power P_(R2) exceeding respective transmitpower limit P_(L2). Therefore, modem(2) is over-limit, and thusrate-limiting. Since modem(2) is over-limit, controller 214 deactivatesmodem(2) in accordance with method 700 or method 1000, thereby causingmodem(2) to transmit at a zero-data rate, and at a correspondinglyreduced transmit power level 1202.

2. Tapered Limits

FIG. 13 is an illustration of an alternative, tapered arrangement forthe fixed modem transmit power limits. As depicted, the taperedarrangement includes progressively decreasing transmit power limitsP_(Li) in respective successive ones of the N modems, where i=1 . . . N.For example, transmit power limit P_(L1) for modem(1) is less thantransmit power limit P_(L2) for modem(2), which is less than transmitpower limit P_(L3), and so on down the line.

In one tapered arrangement, each of the transmit power limits P_(Li) isequal to the APL divided by the total number of modems having transmitpower limits greater than or equal to P_(Li). For example, transmitpower limit P_(L5) is equal to the APL divided by five (5), which is thenumber of modems having transmit power limits greater than or equal toP_(L5). In another tapered arrangement, each transmit power limit P_(Li)is equal to the transmit power limit mentioned above (that is, the APLdivided by the total number of modems having transmit power limitsgreater than or equal to P_(Li)) less a predetermined amount, such asone, two or even three decibels (dB). This permits a safety margin inthe event that the modems tend to transmit at an actual transmit powerlevel that is slightly higher than the respective transmit power limits,before they are deactivated.

Assume a transmit scenario where all of the modems transmit atapproximately the same power, and all of the transmit powers areincreasing over time. Under the tapered arrangement, modem(N)rate-limits first, modem(N−1) rate limits next, modem(N−2) rate-limitsthird, and so on. In response, controller 214 deactivates/deschedulesmodem(N) first, modem(N−1) second, modem(N−3) third, and so on.

VII. Modem Calibration—Determining Gain Factors g(i)

As described above in connection with FIG. 2, each modem 216 i generatesa transmit signal 222 i _(T) having a respective transmit power level.Also, each modem 216 i generates a status report including a modemtransmit power estimate P_(Rep)(i) of the respective transmit powerlevel. Each modem transmit signal 222 i _(T) traverses a respectivetransmit path from modem 222 i to the output of transmit amplifier 228.The respective transmit path includes RF connections, such as cables andconnectors, power combiner/splitter assembly 220, and transmit amplifier228. Therefore, transmit signal 222 i _(T) experiences a respective netpower gain or loss g(i) along the respective transmit path. An examplegain for the above-mentioned transmit path is approximately 29 dB.

Accordingly, the gain or loss g(i) of the respective transmit path maycause the power level of respective transmit signal 222 i _(T) at theoutput of modem 222 i to be different from the transmit power level atthe output of transmit amplifier 228. Therefore, the respective modemtransmit power estimate P_(Rep)(i) may not accurately represent therespective transmit power at the output of transmit amplifier 228. Amore accurate estimate P_(O)(i) of the transmit power at the output oftransmit amplifier 228 (due to modem 222 i), is the reported powerP_(Rep)(i) adjusted by the corresponding gain/loss amount g(i).Therefore, g(i) is referred to as a modem dependent gain correctionfactor g(i), or the modem gain factor g(i) for modem 222 i.

When reported modem transmit power estimate P_(Rep)(i) and modem gaincorrection factor g(i) both represent power terms (as expressed indecibels or Watts, for example), the corrected transmit power estimateP_(O)(i) is given by:P _(O)(i)=g(i)+P _(Rep)(i).

Alternatively, when reported transmit power estimate P_(Rep)(i) andmodem gain correction factor g(i), in Watts, for example, the transmitpower P_(O)(i) is given by:P _(O)(i)=g(i)P _(Rep)(i).

It is useful to be able to calibrate MWT 206 dynamically, to determinethe gain correction factors g(i) corresponding to all of the N modems.Once the factors g(i) are determined, they can be used to calculate moreaccurate individual and aggregate modem transmit power estimates fromthe modem transmit power reports.

FIG. 14 is a flowchart of an example method of calibrating modems 216 inMWT 206. At a first step 1405, controller 214 schedules all N modems 216to transmit data, so as to cause all of the modems to transmit data,concurrently.

At a next step 1410, controller 214 collects status reports 500,including respective reported transmit powers P_(Rep)(i), where irepresents modem i, and i=1 . . . N.

At a next step 1420, controller 214 receives an aggregate transmit powermeasurement P_(Agg) for all of the N modems, for example, as determinedby transmit power monitor 234.

At a next step 1425, controller 214 generates an equation representingthe aggregate transmit power as a cumulative function of reportedtransmit powers P_(Rep)(i) and corresponding unknown, modem dependentgain correction factors g(i). For example, aggregate transmit powerP_(Agg) is represented as:

$P_{Agg} = {\sum\limits_{i = 1}^{N_{N}}{{g(i)}{{P_{Rep}(i)}.}}}$

At a next step 1430, previous steps 1405, 1410, 1420 and 1425 arerepeated N times to generate N simultaneous equations in P_(Rep)(i) andunknown gain correction factors g(i).

At a next step 1435, controller 214 determines the N gain correctionfactors g(i) by solving the N equations generated in step 1430.Determined gain correction factors g(i) are stored in memory 215 of MWT206, and used as needed to adjust/correct modem transmit power estimatesP_(Rep)(i) in the methods of the invention, described below. Method 1400may be scheduled to repeat periodically to update factors g(i) overtime.

VIII. Methods Using Dynamically Updated Transmit Limits

1. Methods Using Energy-Per-Bit Determinations

FIG. 15 is a flowchart of an example method 1500 of operating MWT 206,using dynamically updated individual modem transmit power limits. Inmethod 1500, controller 214 initializes (step 702), schedules anddeschedules active and inactive ones of modems 216 (step 710), andmonitors status reports from the modems (step 712), as described above.At a next step 1502, controller 214 determines whether to modify (forexample, increase or decrease) or maintain the number of active modemsof MWT 206, in order to maximize an aggregate reverse link data rate(that is, the aggregate transmit data rate) without exceeding theaggregate transmit power limit of the MWT.

At a next step 1504, controller 214 increases, decreases, or maintainsthe number of active modems, as necessary, in accordance with step 1502.To increase the number of active modems, controller 214 adds one or morepreviously inactive modems to the active list. Conversely, to decreasethe number of active modems, controller 214 deletes one or morepreviously active modems from the active list.

At a next step 1506, controller 214 updates/adjusts individual transmitpower limits in at least some of modems 216, as necessary. Techniquesfor adjusting individual transmit power limits will be described furtherbelow. In step 1506, the individual transmit power limits are adjustedacross modems 216 such that when all of the individual transmit limitsare combined together into a combined transmit power limit, the combinedtransmit power limit does not exceed the aggregate transmit power limitof MWT 206. Exemplary transmit power limit arrangements that may be usedwith method 1500 are described later in connection with Table 1 and FIG.19. A reason for varying modem transmit power limits in method 1500 isto avoid rate-limiting conditions in the modems. Also, a reason fordeactivating modems (that is, decreasing the number of active modems)includes avoiding rate-limiting conditions so as to increase the overalltransmit data rate on the reverse-link while operating under theaggregate transmit power limit.

At first blush, it might appear that deactivating modems would decrease,not increase, the transmit data rate. However, operating a number ofmodems, for example, 16 modems, at their rate-limited data rates (forexample, at 4800 bps) achieves a lower effective data rate thanoperating a lesser number modems, for example 8 modems, at their fullrates (for example, 9600 bps), even though each case may have the sameaggregate transmit power. This is because the ratio of overheadinformation (used to manage the data calls, for example) toactual/useful data (used by end users, for example) is disadvantageouslygreater for rate limiting modems compared to non-rate limiting modems.

FIG. 16 is a flowchart of an example method 1600 expanding on method1500. Method 1600 includes a step 1602 expanding on step 1502 of method1500. Step 1602 includes further steps 1604 and 1606. At step 1604,controller 214 determines a maximum number N_(Max) of active modems thatcan concurrently transmit at their respective maximum data rates (forexample, at 9600 bps), without exceeding the aggregate transmit powerlimit of MWT 206. It is assumed that N_(Max) is less than or equal to atotal number N of modems 216.

At next step 1606, controller 214 compares the maximum number N_(Max) toa number M of previously active modems (that is, the number of activemodems used in a previous pass through step 710, described above).

A next step 1610, corresponding to step 1504 of method 1500, includesfurther steps 1612, 1614 and 1616. If the maximum number N_(Max) ofactive modems from step 1604 is greater than the number M of previouslyactive modems, the method flow proceeds from step 1606 to next step1612. At step 1612, controller 214 increases the number M of activemodems to the maximum number N_(Max) of active modems. To do this,controller 214 selects an inactive modem to activate from among the Nmodems.

Alternatively, if the maximum number N_(Max) of modems is less than M,then processing proceeds from step 1606 to step 1614. At step 1614,controller 214 decreases the number of active modems. To do this,controller 214 selects an active modem to deactivate. Steps 1612 and1614 together represent an adjusting step (also referred to as amodifying step) where the number M of previously active modems ismodified in preparation for a next pass through steps 710, 712, and soon.

Alternatively, if the maximum number N_(Max) is equal to M, thenprocessing proceeds from step 1606 to step 1616. In step 1616,controller 214 simply maintains the number of active modems at M, forthe next pass through steps 710, 712, and so on.

Processing proceeds from both modifying steps 1612 and 1614 to a next,limit adjusting step 1620. At step 1620, controller 214 increases theindividual transmit power limits in the one or more modems that wereactivated at step 1612. Conversely, controller 214 decreases theindividual power limits in the one or more modems that were deactivatedin step 1614.

The method proceeds from steps 1610 and 1620 back toscheduling/descheduling step 710, and the process described aboverepeats.

FIG. 17 is a flowchart of an example method 1700 of determining themaximum number N_(Max) of active modems using an averageenergy-per-transmitted-bit of the N modems. Method 1700 expands on step1604 of method 1600. At a first step 1702, controller 214 determines anaggregate transmit data rate based on the respective transmit data ratesreported by the N modems. For example, controller 214 adds together allof the transmit data rates reported by the N modems in respective statusreports 500.

At a next step 1704, controller 214 determines an aggregate power levelof transmit signal 230, at the output of transmit amplifier 228. Forexample, controller 214 may receive transmit power measurements (signal236) from transmit power monitor 234. Alternatively, controller 214 mayaggregate individual modem transmit power estimates P_(Rep)(i) (ascorrected using factors g(i)) received from the individual modems inrespective status reports 500.

At a next step 1706, controller 214 determines the averageenergy-per-transmitted-bit across the N modems 216 based on theaggregate data rate and the aggregate transmit power. In one arrangementof the embodiments, controller 214 determines the averageenergy-per-transmitted-bit in accordance the following relationships:BE _(b) _(—) _(avg) =P(t)Δt=E _(T), and, therefore,E _(b) _(—) _(avg)=(P(t)Δt)/B=E _(T) /B,where:

Δt is a predetermined measurement time interval (for example, theduration of a transmitted frame, such as 20 ms),

-   -   B is the aggregate data rate during time interval Δt,    -   E_(b) _(—) _(avg) is the average energy-per-transmitted-bit        during time interval Δt,    -   P(t) is the aggregate transmit power during time interval Δt,        and    -   E_(T) is the total energy of all the bits transmitted during        time interval Δt.

At a next step 1708, controller 214 determines the maximum numberN_(Max) based on the average energy-per-transmitted-bit and theaggregate transmit power limit. In one arrangement, controller 214determines the maximum number N_(Max) in accordance with the followingrelationships:((R _(max) N _(Max) +R _(min)(N−N _(Max)))E _(b) _(—) _(avg) =APL, andthereforeN _(Max)=((APL/E _(b) _(—) _(avg))−P _(min) N)/(R _(max) −R _(min)),where:

-   -   APL is the aggregate transmit power limit of MWT 206 (for        example, 10 or 11 decibel-Watts (dBW)),    -   Rmax is a maximum data rate of the N modems (for example, 9600        bps),    -   Rmin is a minimum data rate of the N modems (for example, 2400        bps),    -   E _(—) _(avg) is the average energy-per-transmitted-bit during        time interval Δt,    -   N is the total number of modems 216, and    -   N_(Max) is the maximum number of active modems to be determined.

FIG. 18 is a flowchart of an example method 1800 of determining themaximum number N_(Max) of active modems, using an individualenergy-per-transmitted-bit for each of modems 216. Method 1800 expandson step 1604 of method 1600. At a first step 1802, controller 214determines an individual energy-per-transmitted-bit E_(b)(i) for eachmodem using modem reports 500. In one arrangement of the embodiment,controller 214 determines each energy-per-transmitted-bit E_(b)(i) inaccordance the following relationship:E _(b)(i)=g(i)P _(Rep)(i)Δt/Bi,where:

-   -   Δt is a predetermined measurement time interval,    -   E_(b)(i) is the individual energy-per-transmitted-bit for modem        i, where i=1 . . . N, over time interval Δt,    -   P_(Rep)(i) is a reported modem transmit power (that is, a        transmit power estimate for modem i), and    -   g(i) is a modem dependent gain correction factor, also referred        to as a gain calibration factor (described above in connection        with FIG. 14), and    -   Bi is the transmit data rate of modem i.

At a step 1804, controller 214 sorts the modems according to theirrespective energy-per-transmitted-bits E_(b)(i).

At a next step 1805, controller 214 determines the maximum numberN_(Max) of active modems based on the individual modemenergy-per-transmitted-bits, using an iterative process. In oneembodiment, the iterative process of step 1805 determines the maximumnumber N_(Max) of active modems that can be supported, using thefollowing equation:

${{APL} = {{\sum\limits_{i = 1}^{N_{Max}}{P_{\max}{E_{b}(i)}}} + {\sum\limits_{i = N_{Max}}^{N}{P_{\min}{E_{b}(i)}}}}},$where:

-   -   APL is the aggregate transmit power limit,    -   P_(max) is the maximum data rate for each modem,    -   P_(min) is the minimum data rate for each modem, and    -   E_(b)(i) is the individual energy-per-transmitted-bit for modem        i.

Step 1805 is now described in further detail. A step 1806 within step1805 is an initializing step in the iterative process, wherein modem 214sets a test number N_(Act) of active modems equal to one (1). Testnumber N_(Act) represents a test, maximum number of active modems. At anext step 1808, modem 214 determines an expected transmit power P_(Exp)using the test number N_(Act) of modems. In step 1808, it is assumedthat the test number N_(Act) of modems having the lowest individualenergy-per-transmitted-bits among the N modems each transmit at amaximum data rate (for example, 9600 bps). In the embodiment mentionedabove, step 1808 determines the expected transmit power in accordancewith the following equation:

${P_{Exp} = {{\sum\limits_{i = 1}^{N_{act}}{P_{\max}{E_{b}(i)}}} + {\sum\limits_{i = N_{act}}^{N}{P_{\min}{E_{b}(i)}}}}},$

At a next step 1809, controller 214 compares the expected transmit powerP_(EXP) to the APL. If P_(Exp)<APL, then more active modems can besupported. Thus, the test number N_(Act) of active modems is incremented(step 1810), and the method proceeds back to step 1808.

Alternatively, if P_(Exp)=APL, then the maximum number N_(Max) of activemodems is set equal to the present test number N_(Act) (step 1812).

Alternatively, if P_(Exp)>APL, then the maximum number N_(Max) is setequal to the previous test number of active modems, that is, N_(Act)−1(step 1814).

If P_(Exp) is neither equal to nor greater than APL then the processreturns to step 1810 and step 1809. At some point a maximum number ofmodems may be reached or exceeded and either step 1812 or 1814,respectively, are reached. The process for recalculating APL checkingthe current N (number of access terminals in use), or checking P_(Exp)relative to APL, may be repeated every so often or on a periodic basisas part of an iterative procedure to prevent overdriving the poweramplifier.

IX. Example Transmit Power Limits

Table 1, below, includes exemplary modem transmit power limits that maybe used in the present invention.

TABLE 1 A No. active B C D modems Active Modem Active Modem Active Modem(Total Limits (dBm) Limits (dBm) Limits (dBm) N = 16) APL = 10 dBW APL =11 dBW APL = 10 dBW 1.0 5.0 5.2 4.2 2.0 5.0 4.6 3.6 3.0 5.0 4.0 3.0 4.05.0 3.5 2.5 5.0 4.0 3.1 2.1 6.0 3.2 2.7 1.7 7.0 2.5 2.3 1.3 8.0 2.0 2.01.0 9.0 1.5 1.7 0.7 10.0 1.0 1.4 0.4 11.0 0.6 1.1 0.1 12.0 0.2 0.9 −0.113.0 −0.1 0.6 −0.4 14.0 −0.5 0.4 −0.6 15.0 −0.8 0.2 −0.8 16.0 −1.0 0.0−1.0

The transmit power limits of Table 1 may be stored in memory 215 of MWT206. Table 1 assumes MWT 206 includes a total of N=16 modems. Each rowof table 1 represents a corresponding number (such as 1, 2, 3, and soon, down the rows) of active ones of the N modems, at any given time.Each row of Column A identifies a given number of active modems. Thenumber of inactive modems corresponding to any given row of Table 1 isthe difference between the total number of modems (16) and the number ofactive modems specified in the given row.

Columns B, C and D collectively represent three different individualtransmit power limit arrangements of the present invention. The transmitlimit arrangement of column B assumes an APL of 10 dBW in MWT 206. Also,the arrangement of column B assumes that, in any given row, all of theactive modems receive a common maximum transmit limit, while all of theinactive modems receive a common minimum transmit limit equal to zero.For example in column B, when the number of active modems is six (6), acommon maximum transmit limit of 3.2 decibel-milliwatt (dBm) isestablished in each of the active modems, and a common minimum transmitlimit of zero is established in each of the ten (10) inactive modems.The sum of the maximum transmit power limits in all of the active modemscorresponding to any given row is equal to the APL.

The transmit limit arrangement of column C assumes an APL of 11 dBW inMWT 206. Also, the arrangement of column C assumes that, for any givennumber of active modems (that is, for each row in Table 1), all of theactive modems receive a common maximum transmit limit, while all of theinactive modems receive a common minimum transmit limit equal to themaximum transmit limit less six (6) dB. For example in column C, whenthe number of active modems is six (6), a maximum transmit limit of 2.7dBm is established in each of the six (6) active modems, and a minimumtransmit limit of (2.7-6) dBm is established in each of the ten (10)inactive modems. The sum of the maximum transmit power limits in all ofthe active modems, together with the sum of the minimum transmit powerlimits in all of the inactive modems, corresponding to any given row isequal to the APL. Since the transmit power limit in each of the inactivemodems is greater than zero, the inactive modems may be able to transmitat respective minimum data rates, or at least at the zero-data rate, inorder to maintain their respective data links active.

The transmit limit arrangement of column D is similar to that of columnC, except a lower APL of 10 dBW is assumed in the arrangement of columnD. The arrangement of column D assumes that, for any given number ofactive modems (that is, for each row in Table 1), all of the activemodems receive a common maximum transmit limit, while all of theinactive modems receive a common minimal transmit limit equal to themaximum transmit limit less six (6) dB. For example, from column D, whenthe number of active modems is six (6), a maximum transmit limit of 1.7dBm is established in each of the active modems, and a transmit limit of(1.7-6) dBm is established in each of the ten (10) inactive modems.

Controller 214 can use the limits specified in Table 1 to establish andadjust individual transmit limits in modems 216 in methods 1500 and1600, described above in connection with FIGS. 15 and 16. For example,assume the transmit limit arrangement of Table 1, column D, is beingused with method 1600. Assume the number of active modems in a previouspass through step 710 is seven. During the previous pass, a transmitlimit of 1.3 dBm is established in each of the seven active modems, anda transmit limit of (1.3-6) dBm is established in the nine inactivemodems (see the entry in column D corresponding to seven active modems).Also assume that in the next pass through steps 1602 and 1614, thenumber of active modems is decreased from seven down to six. Then, atlimit adjusting step 1620, a new transmit limit of 1.7 dB is establishedin each of the six active modems, and a transmit limit of (1.7-6) dB isestablished in each of the ten remaining inactive modems.

FIG. 19 is a graphical representation of the information presented inTable 1. FIG. 19 is a plot of transmit limit power (in dBm) versus thenumber of active modems (labeled as N) for each of the transmit limitarrangements listed in columns B, C and D of Table 1. In FIG. 19, thetransmit limit arrangement of column B is represented by a curve COL B,the limit arrangement of column C is represented by a curve COL C, andthe limit arrangement of column D is represents by a curve COL D.

X. Method of Adjusting Modem Transmit Limits to Track Modem TransmitPowers

FIG. 20 is a flowchart of an example method 2000 of operating MWT 206using dynamically varying individual modem transmit power limits. Method2000 causes each individual modem transmit power limit to track thetransmit power of the modem associated with the transmit power limit.Method 2000 includes steps 702, 710, and 712, as described previously.Steps 710 and 712 are repeated until controller 214 detects anover-limit (OL) modem at a step 2002, based on status reports 500 fromthe modems. When controller 214 detects an over-limit modem at step2002, the controller determines whether or not to adjust or maintain thepresent number of active modems at a step 2004. In this manner, method2000 is reactive to over-limit conditions in the modems of MWT 206. Thisprocessing allows one to increase the number of modems when the channelis good and extra throughput is required.

Step 2004 corresponds to step 1502 of method 1500, mentioned above inconnection with FIG. 15. Step 2004 includes steps 2006, 2008, and 2010.At step 2006, controller 214 determines the aggregate transmit power ofthe N modems 216. For example, controller 214 may receive a transmitpower measurement from transmit power monitor 234. Alternatively,controller 214 may: receive reported transmit power estimates P_(Rep)(i)from the N modems; derive corrected power estimates P_(O)(i) from thereported estimates using gain correction factors g(i); and then combinethe corrected power estimates into an aggregate transmit power estimate,representing the aggregate transmit power of the N modems. Gaincorrection factors g(i) and corrected estimates P_(O)(i) are describedabove in connection with FIG. 14.

At a next step 2008, controller 214 determines whether or not anaggregate transmit power margin (ATM) of MWT 206 is sufficient to permitan increase in the transmit power limit of the over-limit modem. The ATMrepresents the total amount of transmit power headroom existing betweenthe aggregate transmit power and the aggregate transmit power limit. Inone arrangement, the ATM is defined as a difference between theaggregate transmit power of the N modems and the aggregate transmitpower limit.

Step 2008 can include a simple comparison to determine whether theaggregate transmit power is less than the APL by a predetermined amountrequired for increasing the individual transmit limit in the over-limitmodem. An aggregate transmit power margin ATM of between 1 dB and 6 dBmay be considered sufficient for increasing the transmit limit in theover-limit modem.

If the aggregate transmit margin ATM is insufficient to permit anincrease in the transmit limit of the over-limit modem, then controller214 takes further steps in an attempt to free-up or generate moreaggregate transmit margin so that the transmit limit in the over-limitmodem can be increased, and method processing proceeds to a next step2014. Step 2014 includes steps 2016 and 2018 for decreasing the numberof active modems. At step 2016, controller 214 sorts modems 216according to their respective transmit powers. For example, controller214 sorts the modems based on the respective reported transmit powerestimates P_(Rep)(i), as corrected by respective gain factors g(i).

At next step 2018, controller 214 deactivates a modem having thegreatest transmit power among the active modems. The eventual result ofdeactivating the modem in step 2018 is to reduce the aggregate transmitpower of the N modems, and thus correspondingly increase the aggregatetransmit margin ATM. Processing then proceeds to a transmit limitadjusting step 2020.

Returning again to step 2008, if the aggregate transmit margin ATM issufficient to increase the transmit limit in the over-limit modem, thenprocessing proceeds to step 2010. At step 2010, controller 214determines whether or not the aggregate transmit margin is sufficient toincrease the transmit limits in both the over-limit modem and anotherinactive modem. In other words, step 2010 determines whether there issufficient transmit margin (for example, at least 3 dB of transmitmargin) to increase the number of active modems. If not (that is, thereis insufficient aggregate transmit margin to increase the number ofactive modems), then processing proceeds to a step 2022, wherein thenumber of active modems is maintained. The method proceeds from step2022 to transmit limit adjusting step 2020.

On the other hand, if the aggregate transmit margin ATM is sufficient toincrease the number of active modems or increase the transmit limit inthe over-limit modem, then processing proceeds from step 2010 to a nextstep 2024, wherein the number of active modems is increased or powerincreased to an active modem. That is, if there is sufficient transmitmargin then one is free to chose to apply this extra power to any modemdesired, regardless of whether one is over limit or not. _Processingproceeds from step 2024 to limit adjusting step 2020. Steps 2014, 2022and 2024 of method 2000 correspond to adjusting step 1504 of method1500, while step 2020 corresponds to step 1506 of method 1500.

At limit adjusting step 2020, controller 214 adjusts the individualtransmit power limits in at least some of the N modems based on theaggregate transmit power limit, the aggregate transmit power margin ATM,and the respective power estimates from the N modems, thereby causingeach individual power limit to track the corresponding individual modemtransmit power. Flow proceeds from step 2020 back to step 710.

FIG. 21 is a flow chart of an example method 2100 expanding on limitadjusting step 2020 of method 2000. Processing proceeds from modemdeactivating step 2018 of method 2000 (from FIG. 20) to a step 2105 ofmethod 2100. At step 2105, controller 214 reduces the individualtransmit power limit in the modem deactivated in step 2018. Controller214 may reduce the individual transmit limit by 6 dB, for example. Thispermits a corresponding increase in the transmit power limit of theover-limit modem (determined in step 2002 of method 2000), withoutaltering a combined transmit power limit of all of the N modems. Thecombined transmit power limit of all of the N modems is the sum of the Nindividual transmit power limits. The combined transmit power limitshould not exceed the aggregate transmit power limit.

The method proceeds from modem activating step 2024 of method 2000 (fromFIG. 20) to a step 2110 of method 2100. At step 2110, controller 214increases the individual transmit limit in the modem activated in step2024. Controller 214 may increase the individual transmit limit in theactivated modem by an amount equal to the transmit power margin, less atleast a few dB needed to increase the transmit limit in the over-limitmodem.

Processing proceeds from steps 2105 and 2110, and from maintaining step2022 of method 2000 (from FIG. 20), to a step 2115 of method 2100. Atstep 2115, controller 214 adjusts the individual transmit power limitsin at least some of the N modems based on the aggregate transmit powerlimit and the respective transmit power estimates from the N modems, tocause each individual transmit power limit to track its correspondingmodem transmit power. The transmit power limits are adjusted so thatwhen all of the individual transmit power limits are combined into acombined transmit power limit, the combined transmit power limit is lessthan or equal to the aggregate transmit power limit. Also, eachindividual transmit power limit is preferably greater than thecorresponding individual modem transmit power, to avoid over-limitconditions in the modems. To achieve the results mentioned above,controller 214 apportions the aggregate transmit margin ATM across the Nmodems as necessary, and increases the transmit limit in the over-limitmodem.

FIG. 22 is a flow chart of an example method 2200 expanding on step2115. At a first step 2205, controller 214 determines the aggregatetransmit margin ATM. This step may be optional because the aggregatetransmit margin ATM may also be determined previously at step 2006.

At a next step 2210, controller 214 divides the aggregate transmitmargin among at least some of the N modems to derive the individualtransmit limits. In one arrangement, the aggregate transmit margin isevenly divided among the N modems. For example, assume the aggregatetransmit margin is divided into N equal portions, where each portion isequal to X dB. Then the individual transmit limit for each modem 222 imay be derived by adding X dB to the estimated transmit power P_(Rep)(i)of the modem. This produces a transmit limit in modem 222 i that exceedsthe estimated transmit power by X dB, and thus, likely avoids anover-limit condition in the modem. Also, as this process is repeatedover time, each individual transmit power limit tracks the transmitpower of the corresponding modem. That is, each transmit power limittends to increase and decrease with the corresponding modem transmitpower.

FIG. 23A is an example plot of power versus modem index (i) identifyingrespective ones of modems 216 being controlled in accordance with method2000. FIG. 23A corresponds to an example transmit scenario in MWT 206occurring at a first time t₁. Modem(1) has a respective modem transmitpower P₁ and a respective transmit power limit P_(L1), modem(2) has arespective modem transmit power P₂ and a respective transmit power limitP_(L2), and so on. The depicted transmit powers P_(i) can representactual modems transmit powers, reported modem transmit powersP_(Rep)(i), or adjusted modem transmit powers P_(O)(i). As depicted, therespective modem transmit power limits vary from modem to modem inaccordance with the respective modem transmit powers. Each modemtransmit power limit P_(Li) is slightly greater than the correspondingmodem transmit power P_(i).

-   -   FIG. 23B corresponds to an example transmit scenario in MWT 206        occurring at a second time t₂, some time after first time t₁.        The respective modem transmit powers depicted in FIG. 23B have        changed with respect to FIG. 23A, however, the respective        transmit power limits have also changed in correspondence with        the transmit powers. The power limits track the changes.

FIG. 23C corresponds to an example transmit scenario in MWT 206 whereinthe transmit power P₂ of modem(2) exceeds the transmit power limit. Thiscorresponds to a possible over-limit condition of modem(2). In response,method 2000 increases the transmit power limit in modem(2) to avoid theover-limit condition, and redistributes any remaining aggregate transmitpower margin among the other modems.

FIG. 23D corresponds to an example transmit scenario in MWT 206 aftermethod 2000 has reacted to the over-limit scenario of FIG. 23C. In FIG.23D, transmit power limit P_(L2) of modem(2) has been adjusted by method2000 to exceed transmit power P₂ of modem(2). Also, the decrease inmodem transmit power P₃ provides a corresponding increase in theaggregate transmit power margin ATM. The increased ATM is allocatedacross the modems.

XI. MWT Computer Controller

FIG. 24 is a functional block diagram of an example controller (whichcan also be a plurality of controllers) 2400 representing controller214. Controller 2400 includes a series of controller modules forperforming the various method steps of the embodiments discussed above.

A scheduler/de-scheduler 2402 schedules active modems to transmitpayload data, and to deschedule inactive modems, while a call manager2404 establishes data calls and tears-down data calls over the pluralityof modems 216.

A status monitor 2406 monitors status reports from modems 216, forexample, to determine when various ones of the modems are over-limit,and collects modem transmit data rates and transmit powers. Statusmonitor 2406 may also determine an aggregate data rate and an aggregatetransmit power based on the modem reports.

A deactivator/activator module 2408 acts to deactivate over-limit ones(in the fixed limit arrangement of the present invention) of the modems(for example by removing the modems from the active list) and toactivate deactivated ones of the modems by reinstating the modems on theactive list. Module 2408 also activates/deactivates selected ones of themodems in accordance with steps 1504, 1612, 1614, 2014, and 2024 ofmethods 1500, 1600, and 2000.

A limit calculator 2410 operates to calculate/derive transmit powerlimits for each of the modems 216. Limit calculator also accessespredetermined transmit power limits stored in memory 215, for example.Limit calculator 2410 calculates transmit power limits in accordancewith steps 1506, 1620, and 2020.

An initializer 2412 is used to supervise/manage initialization of thesystem, such as establishing initial transmit power limits in eachmodem, setting up calls over each modem, initializing various lists andqueues in MWT 206, and so on; a modem interface 2414 receives data fromand transmits data to modems 216; and a network interface 2416 operatesto receive and transmit data over interface 210.

A module 2420 is used for determining whether to adjust the number ofactive modems in accordance with steps 1502, 1602, and 2004 of methods1500, 1600 and 2400. Module 2420 includes a sub-module 2422 fordetermining a maximum number of active modems that can be supportedbased on either an average-energy-per-transmitted-bit or individualmodem energy-per-transmitted-bits. Sub-module 2422 includes comparinglogic (such as a comparator) configured to operate in accordance withcomparing step 1606 of method 1600. Module 2420 also includessub-modules 2424 and 2426 for determining theaverage-energy-per-transmitted-bit and the individual modemenergy-per-transmitted-bits, respectively. Sub-modules 2424 and 2426, oralternatively, status monitor 2406, also determine an aggregate datarate and an aggregate transmit power based on modem reports. Module 2420also includes a sub-module 2428 for determining the sufficiency of anaggregate transmit power margin ATM in accordance with steps 2008 and2010 of method 2000.

A calibration module 2440 controls calibration in MWT 206 in accordancewith method 1400, for example. The calibration module includes anequation generator to generate simultaneous equations and an equationsolver to solve the equations to determine modem correction factorsg(i). The calibration module can also call/incorporate other modules, asnecessary, to perform calibration of MWT 206.

A software interface 2450 is used for interconnecting all of the abovementioned modules to one another.

Features of the present invention can be performed and/or controlled byprocessor/controller 214, which in effect comprises a programmable orsoftware controllable element, device, or computer system. Such acomputer system includes, for example, one or more processors that areconnected to a communication bus. Although telecommunication-specifichardware can be used to implement the present invention, the followingdescription of a general purpose type computer system is provided forcompleteness.

The computer system can also include a main memory, preferably a randomaccess memory (RAM), and can also include a secondary memory and/orother memory. The secondary memory can include, for example, a hard diskdrive and/or a removable storage drive. The removable storage drivereads from and/or writes to a removable storage unit in a well knownmanner. The removable storage unit, represents a floppy disk, magnetictape, optical disk, and the like, which is read by and written to by theremovable storage drive. The removable storage unit includes a computerusable storage medium having stored therein computer software and/ordata.

The secondary memory can include other similar means for allowingcomputer programs or other instructions to be loaded into the computersystem. Such means can include, for example, a removable storage unitand an interface. Examples of such can include a program cartridge andcartridge interface (such as that found in video game devices), aremovable memory chip (such as an EPROM, or PROM) and associated socket,and other removable storage units and interfaces which allow softwareand data to be transferred from the removable storage unit to thecomputer system.

The computer system can also include a communications interface. Thecommunications interface allows software and data to be transferredbetween the computer system and external devices. Software and datatransferred via the communications interface are in the form of signalsthat can be electronic, electromagnetic, optical or other signalscapable of being received by the communications interface. As depictedin FIG. 2, processor 214 is in communications with memory 215 forstoring information. Processor 214, together with the other componentsof MWT 206 discussed in connection with FIG. 2, performs the methods ofthe present invention.

In this document, the terms “computer program medium” and “computerusable medium” are used to generally refer to media such as a removablestorage device, a removable memory chip (such as an EPROM, or PROM)within MWT 206, and signals. Computer program products are means forproviding software to the computer system.

Computer programs (also called computer control logic) are stored in themain memory and/or secondary memory. Computer programs can also bereceived via the communications interface. Such computer programs, whenexecuted, enable the computer system to perform certain features of thepresent invention as discussed herein. For example, features of the flowcharts depicted in FIGS. 7-10, 14-18, and 20-22, can be implemented insuch computer programs. In particular, the computer programs, whenexecuted, enable processor 214 to perform and/or cause the performanceof features of the present invention. Accordingly, such computerprograms represent controllers of the computer system of MWT 206, andthus, controllers of the MWT.

Where embodiments are implemented using software, the software can bestored in a computer program product and loaded into the computer systemusing the removable storage drive, the memory chips or thecommunications interface. The control logic (software), when executed byprocessor 214, causes processor 214 to perform certain functions of theinvention as described herein.

Features of the invention may also or alternatively be implementedprimarily in hardware using, for example, a software-controlledprocessor or controller programmed to perform the functions describedherein, a variety of programmable electronic devices, or computers, amicroprocessor, one or more digital signal processors (DSP), dedicatedfunction circuit modules, and hardware components such as applicationspecific integrated circuits (ASICs) or programmable gate arrays (PGAs).Implementation of the hardware state machine so as to perform thefunctions described herein will be apparent to persons skilled in therelevant art(s).

The previous description of the preferred embodiments is provided toenable a person skilled in the art to make or use the present invention.While the invention has been particularly shown and described withreference to embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the invention.

XII. Conclusion

The present invention has been described above with the aid offunctional building blocks illustrating the performance of specifiedfunctions and relationships thereof. The boundaries of these functionalbuilding blocks have been arbitrarily defined herein for the convenienceof the description. Alternate boundaries can be defined so long as thespecified functions and relationships thereof are appropriatelyperformed. Any such alternate boundaries are thus within the scope andspirit of the claimed invention. One skilled in the art will recognizethat these functional building blocks can be implemented by discretecomponents, application specific integrated circuits, processorsexecuting appropriate software and the like or many combinationsthereof. Thus, the breadth and scope of the present invention should notbe limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

1. A method of controlling transmit power in a data terminal constrainedto operate within an aggregate transmit power limit, the data terminalincluding N wireless modems having their respective transmit outputscombined to produce an aggregate transmit output, the method comprising:(a) establishing an individual transmit power limit in each of the Nmodems; (b) scheduling each of a plurality of the N modems to transmitrespective data; (c) receiving a respective, reported transmit powerestimate from each of the N modems; and (d) adjusting the individualtransmit power limits in at least some of the N modems based on theaggregate transmit power limit and the respective transmit powerestimates from the N modems, to cause each individual transmit powerlimit to track a corresponding individual modem transmit power.
 2. Themethod of claim 1, wherein step (d) comprises adjusting the individualtransmit power limits such that when the N individual transmit powerlimits are combined into a combined transmit power limit, the combinedtransmit power limit is less than or equal to the aggregate transmitpower limit, and each individual transmit power limit is greater thanthe corresponding individual modem transmit power.
 3. The method ofclaim 1, further comprising, prior to step (a), establishing anindividual wireless communication link between each of the N modems anda remote station, each communication link including a forward link and areverse link.
 4. The method of claim 3, wherein each wirelesscommunication link is a Code Division Multiple Access (CDMA)communication link.
 5. In a data terminal constrained to operate withinan aggregate transmit power limit, the data terminal including Nwireless modems having their respective transmit outputs combined toproduce an aggregate transmit output, the modems having individualtransmit power limits to limit their respective transmit powers, themodems reporting respective transmit power estimates, a method ofderiving the individual transmit power limits, comprising: (b)determining an aggregate transmit power encompassing all of the Nmodems; (b) deriving an aggregate transmit power margin based on adifference between the aggregate transmit power and the aggregatetransmit power limit; and (c) dividing the aggregate transmit powermargin among the N modems to produce, for each of the N modems, anindividual transmit power limit that is greater than the correspondingtransmit power estimate for each modem.
 6. The method of claim 5,wherein step (c) comprises dividing the aggregate transmit power equallyamong the N modems.
 7. The method of claim 5, further comprising, priorto step (a): producing a corrected transmit power estimate from eachtransmit power estimate using a corresponding predetermined, modem gaincorrection factor; and performing steps (a) and (c) using the correctedtransmit power estimates.
 8. An apparatus for controlling a wirelessterminal constrained to operate within an aggregate transmit powerlimit, the wireless terminal including N wireless modems having theirrespective transmit outputs combined to produce an aggregate transmitoutput, comprising: means for establishing an individual transmit powerlimit in each of the N modems; means for scheduling each of a pluralityof the N modems to transmit respective data; means for receiving arespective, reported transmit power estimate from each of the N modems;and means for adjusting the individual transmit power limits in at leastsome of the N modems based on the aggregate transmit power limit and therespective transmit power estimates from the N modems, to cause eachindividual transmit power limit to track a corresponding individualmodem transmit power.
 9. The apparatus of claim 8, wherein the adjustingmeans comprises means for adjusting the individual transmit power limitssuch that when the N individual transmit power limits are combined intoa combined transmit power limit, the combined transmit power limit isless than or equal to the aggregate transmit power limit, and eachindividual transmit power limit is greater than the correspondingindividual modem transmit power.
 10. An apparatus for deriving modemtransmit limits in a wireless terminal constrained to operate within anaggregate transmit power limit, the wireless terminal including Nwireless modems having their respective transmit outputs combined toproduce an aggregate transmit output, the modems having individualtransmit power limits to limit their respective transmit powers, themodems reporting respective transmit power estimates, comprising: meansfor determining an aggregate transmit power encompassing all of the Nmodems; means for deriving an aggregate transmit power margin based on adifference between the aggregate transmit power and the aggregatetransmit power limit; and means for dividing the aggregate transmitpower margin among the N modems to produce, for each of the N modems, anindividual transmit power limit that is greater than the correspondingtransmit power estimate for each modem.
 11. The apparatus of claim 10,wherein the dividing means comprises dividing the aggregate transmitpower equally among the N modems.
 12. A computer-readable medium storinginstructions for controlling transmit power in a data terminalconstrained to operate within an aggregate transmit power limit, thedata terminal including N wireless modems having their respectivetransmit outputs combined to produce an aggregate transmit output, theinstructions comprising: instructions to establish an individualtransmit power limit in each of the N modems; instructions to scheduleeach of a plurality of the N modems to transmit respective data;instructions to receive a respective, reported transmit power estimatefrom each of the N modems; and instructions to adjust the individualtransmit power limits in at least some of the N modems based on theaggregate transmit power limit and the respective transmit powerestimates from the N modems, to cause each individual transmit powerlimit to track a corresponding individual modem transmit power.